UV photoemission study of dye/AgBr interfaces in relation to spectral sensitization

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Abstract
The electronic structure of dye/AgBr interfaces has been studied by UV photoelectron spectroscopy for several merocyanine dye films vacuum deposited on AgBr films. With these results energy diagrams of interfaces were obtained, which include the vacuum level, Fermi level, top of the valence band, and bottom of the conduction band of AgBr, and the energy levels of the highest occupied molecular orbital and the lowest unoccupied molecular orbital of the dyes. These energy diagrams were consistent with the trend in the measured abilities of these dyes for spectral sensitization in the framework of the electron-transfer mechanism. The vacuum level of AgBr was found to be significantly lowered by dye deposition. We discuss the factors determining the electronic structure, including the origin of the electric double layer at the interface, which gives rise to the shift of the vacuum level.